Compression packing is used to control leakage about shafts. Compression packing generally has an assembly of radially expandable rings that coaxially surrounds a shaft. Such packing is used in a wide variety of applications including packing for pumps, valves and hydraulic and pneumatic equipment. Shafts are conventionally surrounded by a compartment generally extending outward from the housing surrounding the shaft referred to as a “packing box” or “stuffing box.” The interior of the stuffing box is generally of a diameter sufficiently greater than the shaft to accommodate compressible “packing rings” and a number of relatively non-compressible auxiliary rings.
The packing rings in the stuffing box are compressed by an annular “gland” fitted about the shaft and bolted to the exterior of the stuffing box. Axial compressive loading force from the gland is applied to the packing rings, causing them to expand radially to some extent, forcing the inner peripheries against the outer surface of the shaft and causing the packing rings to fill the stuffing box. This aims to prevent or minimize the escape of the contents of the housing at the intersection of the shaft and housing. Tightening of the gland is conventionally by means of a flange. Bolts pass through the flange and are threaded into threaded holes in the stuffing box. When the gland is tightened, the packing rings are further compressed in the stuffing box.
The auxiliary rings employed in packing sets include bushing rings, excluder rings, spacer rings, gaskets, restriction bushings, lantern rings, flush rings, or combinations thereof. These auxiliary rings are generally constructed of non-compressible materials and aid in the retention and/or function of the compressible packing rings. Traditionally, when maintenance is performed on a stuffing box assembly, the entire apparatus must be disassembled and the rings must be removed from the stuffing box, new rings put in place, and the apparatus is reassembled.
Additionally, this requires the removal of machine parts that surround or are adjacent to the part being sealed, such as the rotary member, in order to allow ample access room to permit ring replacement. Disassembly and re-assembly of such parts often require a great expenditure of time and labor, along with a consequent monetary cost. For example, where a shaft extends from a housing, the exterior bearing or journal member for such shaft, as well as the coupling parts to the shaft and external parts of the housing, may have to be removed before the integral seals can be brought into access position for removal. The cost for such repair may be considerable, as product is lost during the interval of machine down-time.
One conventional solution to this problem is to provide split-ring elements, which are used in many applications wherein integral solid seals would be difficult or time-consuming to install. Employment of split seals may reduce the time for replacing a seal from 24 hours (if a solid integral seal was employed) to less than an hour. Split seals can be slipped around the shaft without dismantling the apparatus and are frequently bolted together, squeezed together with an “O” ring or squeezed together on a taper.
Bolted split seal elements are relatively expensive and generally require a large amount of space for the seal. Split seal elements that are squeezed together with an “O” ring are generally limited to use with respect to shafts having a low rotational speed, since centrifugal forces tend to open the split halves at high rotational speeds. While split seal elements which are squeezed together with a taper are somewhat more adaptable, the alignment of surfaces has to be near perfect in order to prevent leakage. Further, while generally providing for more flexibility in the shaft diameter ranges in which they may be employed, split seal elements like integral-solid seals suffer from a relatively inflexibility in the array of rotary diameters on which they may be employed.